Method of manufacture for single crystal acoustic resonator devices using micro-vias

ABSTRACT

A method of manufacture for an acoustic resonator device. The method includes forming a nucleation layer characterized by nucleation growth parameters overlying a substrate and forming a strained piezoelectric layer overlying the nucleation layer. The strained piezoelectric layer is characterized by a strain condition and piezoelectric layer parameters. The process of forming the strained piezoelectric layer can include an epitaxial growth process configured by nucleation growth parameters and piezoelectric layer parameters to modulate the strain condition in the strained piezoelectric layer. By modulating the strain condition, the piezoelectric properties of the resulting piezoelectric layer can be adjusted and improved for specific applications.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application claims priority to and is a continuation of U.S.patent application Ser. No. 15/221,358 (Attorney Docket No.969RO0007US1), filed Jul. 27, 2016, which is a continuation-in-partapplication of U.S. patent application Ser. No. 15/068,510, (AttorneyDocket No. 969RO0007US), filed Mar. 11, 2016, now issued as U.S. Pat.No. 10,217,930 on Feb. 26, 2019. The present application alsoincorporates by reference, for all purposes, the following concurrentlyfiled patent applications, all commonly owned: U.S. patent applicationSer. No. 14/298,057, (Attorney Docket No. A969RO-000100US) titled“RESONANCE CIRCUIT WITH A SINGLE CRYSTAL CAPACITOR DIELECTRIC MATERIAL,”filed Jun. 6, 2014, U.S. patent application Ser. No. 14/298,076,(Attorney Docket No. A969RO-000200US) titled “METHOD OF MANUFACTURE FORSINGLE CRYSTAL CAPACITOR DIELECTRIC FOR A RESONANCE CIRCUIT,” filed Jun.6, 2014, U.S. patent application Ser. No. 14/298,100, (Attorney DocketNo. A969RO-000300US) titled “INTEGRATED CIRCUIT CONFIGURED WITH TWO ORMORE SINGLE CRYSTAL ACOUSTIC RESONATOR DEVICES,” filed Jun. 6, 2014,U.S. patent application Ser. No. 14/341,314, (Attorney Docket No.:A969RO-000400US) titled “WAFER SCALE PACKAGING,” filed Jul. 25, 2014,U.S. patent application Ser. No. 14/449,001, (Attorney Docket No.:A969RO-000500US) titled “MOBILE COMMUNICATION DEVICE CONFIGURED WITH ASINGLE CRYSTAL PIEZO RESONATOR STRUCTURE,” filed Jul. 31, 2014, and U.S.patent application Ser. No. 14/469,503, (Attorney Docket No.:A969RO-000600US) titled “MEMBRANE SUBSTRATE STRUCTURE FOR SINGLE CRYSTALACOUSTIC RESONATOR DEVICE,” filed Aug. 26, 2014.

BACKGROUND OF THE INVENTION

The present invention relates generally to electronic devices. Moreparticularly, the present invention provides techniques related to amethod of manufacture for bulk acoustic wave resonator devices, singlecrystal bulk acoustic wave resonator devices, single crystal filter andresonator devices, and the like. Merely by way of example, the inventionhas been applied to a single crystal resonator device for acommunication device, mobile device, computing device, among others.

Mobile telecommunication devices have been successfully deployedworld-wide. Over a billion mobile devices, including cell phones andsmartphones, were manufactured in a single year and unit volumecontinues to increase year-over-year. With ramp of 4G/LTE in about 2012,and explosion of mobile data traffic, data rich content is driving thegrowth of the smartphone segment—which is expected to reach 2 B perannum within the next few years. Coexistence of new and legacy standardsand thirst for higher data rate requirements is driving RF complexity insmartphones. Unfortunately, limitations exist with conventional RFtechnology that is problematic, and may lead to drawbacks in the future.

From the above, it is seen that techniques for improving electronicdevices are highly desirable.

BRIEF SUMMARY OF THE INVENTION

According to the present invention, techniques generally related toelectronic devices are provided. More particularly, the presentinvention provides techniques related to a method of manufacture forbulk acoustic wave resonator devices, single crystal resonator devices,single crystal filter and resonator devices, and the like. Merely by wayof example, the invention has been applied to a single crystal resonatordevice for a communication device, mobile device, computing device,among others.

In an example, the present invention provides a method for fabricating abulk acoustic wave resonator device. This method can include providing apiezoelectric substrate having a substrate surface region. This piezoelectric substrate can have a piezoelectric layer formed overlying aseed substrate. A topside metal electrode can be formed overlying aportion of the substrate surface region. The method can include forminga topside micro-trench within a portion of the piezoelectric layer andforming one or more bond pads overlying one or more portions of thepiezoelectric layer. A topside metal can be formed overlying a portionof the piezoelectric layer. This topside metal can include a topsidemetal plug, or a bottom side metal plug, formed within the topsidemicro-trench and electrically coupled to at least one of the bond pads.

In an example, the present invention provides a method of manufacturefor an acoustic resonator device. The method includes forming anucleation layer characterized by nucleation growth parameters overlyinga substrate and forming a strained piezoelectric layer overlying thenucleation layer. The strained piezoelectric layer is characterized by astrain condition and piezoelectric layer parameters. The process offorming the strained piezoelectric layer can include an epitaxial growthprocess configured by nucleation growth parameters and piezoelectriclayer parameters to modulate the strain condition in the strainedpiezoelectric layer. By modulating the strain condition, thepiezoelectric properties of the piezoelectric layer can be adjusted andimproved for specific applications.

In an example, the method can include thinning the seed substrate toform a thinned seed substrate. A first backside trench can be formedwithin the thinned seed substrate and underlying the topside metalelectrode. A second backside trench can be formed within the thinnedseed substrate and underlying the topside micro-trench. Also, the methodincludes forming a backside metal electrode underlying one or moreportions of the thinned seed substrate, within the first backsidetrench, and underlying the topside metal electrode; and forming abackside metal plug underlying one or more portions of the thinnedsubstrate, within the second backside trench, and underlying the topsidemicro-trench. The backside metal plug can be electrically coupled to thetopside metal plug and the backside metal electrode. The topsidemicro-trench, the topside metal plug, the second backside trench, andthe backside metal plug form a micro-via. In a specific example, bothbackside trenches can be combined in one trench, where the sharedbackside trench can include the backside metal electrode underlying thetopside metal electrode and the backside metal plug underlying thetopside micro-trench.

In an example, the method can include providing a top cap structure,wherein the top cap structure including an interposer substrate with oneor more through-via structures electrically coupled to one or more topbond pads and one or more bottom bond pads. The top cap structure can bebonded to the piezoelectric substrate, while the one or more bottom bondpads can be electrically coupled to the one or more bond pads and thetopside metal. A backside cap structure can be bonded to the thinnedseed substrate such that the backside cap structure is configuredunderlying the first and second backside trenches, and one or moresolder balls formed overlying the one or more top bond pads.

In an alternative example, the method can include providing a top capstructure, wherein the top cap structure including an interposersubstrate with one or more blind via structures electrically coupled toone or more bottom bond pads. The top cap structure can be bonded to thepiezoelectric substrate, while the one or more bottom bond pads areelectrically coupled to the one or more bond pads and the topside metal.The method can include thinning the top cap structure to expose the oneor more blind vias. One or more top bond pads can be formed overlyingand electrically coupled to the one or more blind vias, and one or moresolder balls can be formed overlying the one or more top bond pads.

In an alternative example, the method can include providing a top capstructure, wherein the top cap structure including a substrate with oneor more bottom bond pads. The top cap structure can be bonded to thepiezoelectric substrate, while the one or more bottom bond pads areelectrically coupled to the one or more bond pads and the topside metal.A backside cap structure can be bonded to the thinned seed substratesuch that the backside cap structure is configured underlying the firstand second backside trenches. The method can include forming one or morebackside bond pads within one or more portions of the backside capstructure. These one or more of the backside bond pads can beelectrically coupled to the backside metal plug. One or more solderballs can be formed underlying the one or more backside bond pads.

In an alternative example, the present invention can provide a methodfor fabricating a top cap or bottom cap free structure, wherein thethinned device is assembled into the final package on the die level.Compared to the examples previously described, the top cap or bottom capfree structure may omit the steps of bonding a top cap structure to thepiezoelectric substrate or the steps of bonding a backside cap structureto the thinned substrate.

One or more benefits are achieved over pre-existing techniques using theinvention. In particular, the present device can be manufactured in arelatively simple and cost effective manner while using conventionalmaterials and/or methods according to one of ordinary skill in the art.Using the present method, one can create a reliable single crystal basedacoustic filter or resonator using multiple ways of three-dimensionalstacking through a wafer level process. Such filters or resonators canbe implemented in an RF filter device, an RF filter system, or the like.Depending upon the embodiment, one or more of these benefits may beachieved.

A further understanding of the nature and advantages of the inventionmay be realized by reference to the latter portions of the specificationand attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more fully understand the present invention, reference ismade to the accompanying drawings. Understanding that these drawings arenot to be considered limitations in the scope of the invention, thepresently described embodiments and the presently understood best modeof the invention are described with additional detail through use of theaccompanying drawings in which:

FIG. 1A is a simplified diagram illustrating an acoustic resonatordevice having topside interconnections according to an example of thepresent invention.

FIG. 1B is a simplified diagram illustrating an acoustic resonatordevice having bottom-side interconnections according to an example ofthe present invention.

FIG. 1C is a simplified diagram illustrating an acoustic resonatordevice having interposer/cap-free structure interconnections accordingto an example of the present invention.

FIG. 1D is a simplified diagram illustrating an acoustic resonatordevice having interposer/cap-free structure interconnections with ashared backside trench according to an example of the present invention.

FIGS. 2 and 3 are simplified diagrams illustrating steps for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention.

FIG. 4A is a simplified diagram illustrating a step for a methodcreating a topside micro-trench according to an example of the presentinvention.

FIGS. 4B and 4C are simplified diagrams illustrating alternative methodsfor conducting the method step of forming a topside micro-trench asdescribed in FIG. 4A.

FIGS. 4D and 4E are simplified diagrams illustrating an alternativemethod for conducting the method step of forming a topside micro-trenchas described in FIG. 4A.

FIGS. 5 to 8 are simplified diagrams illustrating steps for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention.

FIG. 9A is a simplified diagram illustrating a method step for formingbackside trenches according to an example of the present invention.

FIGS. 9B and 9C are simplified diagrams illustrating an alternativemethod for conducting the method step of forming backside trenches, asdescribed in FIG. 9A, and simultaneously singulating a seed substrateaccording to an example of the present invention.

FIG. 10 is a simplified diagram illustrating a method step formingbackside metallization and electrical interconnections between top andbottom sides of a resonator according to an example of the presentinvention.

FIGS. 11A and 11B are simplified diagrams illustrating alternative stepsfor a method of manufacture for an acoustic resonator device accordingto an example of the present invention.

FIGS. 12A to 12E are simplified diagrams illustrating steps for a methodof manufacture for an acoustic resonator device using a blind viainterposer according to an example of the present invention.

FIG. 13 is a simplified diagram illustrating a step for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention.

FIGS. 14A to 14G are simplified diagrams illustrating method steps for acap wafer process for an acoustic resonator device according to anexample of the present invention.

FIGS. 15A-15E are simplified diagrams illustrating method steps formaking an acoustic resonator device with shared backside trench, whichcan be implemented in both interposer/cap and interposer free versions,according to examples of the present invention.

FIG. 16 is a simplified flow diagram illustrating a method formanufacturing an acoustic resonator device according to an example ofthe present invention.

FIG. 17 is a simplified graph illustrating the results of forming apiezoelectric layer for an acoustic resonator device according to anexample of the present invention. The graph highlights the ability of totailor the acoustic properties of the material for a given Aluminum molefraction. Such flexibility allows for the resulting resonator propertiesto be tailored to the individual application.

FIG. 18A is a simplified diagram illustrating a method for forming apiezoelectric layer for an acoustic resonator device according to anexample of the present invention.

FIG. 18B is a simplified diagram illustrating a method for forming apiezoelectric layer for an acoustic resonator device according to anexample of the present invention.

FIG. 18C is a simplified diagram illustrating a method for forming apiezoelectric layer for an acoustic resonator device according to anexample of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, techniques generally related toelectronic devices are provided. More particularly, the presentinvention provides techniques related to a single crystal acousticresonator using wafer level technologies. Merely by way of example, theinvention has been applied to a resonator device for a communicationdevice, mobile device, computing device, among others.

FIG. 1A is a simplified diagram illustrating an acoustic resonatordevice 101 having topside interconnections according to an example ofthe present invention. As shown, device 101 includes a thinned seedsubstrate 112 with an overlying single crystal piezoelectric layer 120,which has a micro-via 129. The micro-via 129 can include a topsidemicro-trench 121, a topside metal plug 146, a backside trench 114, and abackside metal plug 147. Although device 101 is depicted with a singlemicro-via 129, device 101 may have multiple micro-vias. A topside metalelectrode 130 is formed overlying the piezoelectric layer 120. A top capstructure is bonded to the piezoelectric layer 120. This top capstructure includes an interposer substrate 119 with one or morethrough-vias 151 that are connected to one or more top bond pads 143,one or more bond pads 144, and topside metal 145 with topside metal plug146. Solder balls 170 are electrically coupled to the one or more topbond pads 143.

The thinned substrate 112 has the first and second backside trenches113, 114. A backside metal electrode 131 is formed underlying a portionof the thinned seed substrate 112, the first backside trench 113, andthe topside metal electrode 130. The backside metal plug 147 is formedunderlying a portion of the thinned seed substrate 112, the secondbackside trench 114, and the topside metal 145. This backside metal plug147 is electrically coupled to the topside metal plug 146 and thebackside metal electrode 131. A backside cap structure 161 is bonded tothe thinned seed substrate 112, underlying the first and second backsidetrenches 113, 114. Further details relating to the method of manufactureof this device will be discussed starting from FIG. 2.

FIG. 1B is a simplified diagram illustrating an acoustic resonatordevice 102 having backside interconnections according to an example ofthe present invention. As shown, device 101 includes a thinned seedsubstrate 112 with an overlying piezoelectric layer 120, which has amicro-via 129. The micro-via 129 can include a topside micro-trench 121,a topside metal plug 146, a backside trench 114, and a backside metalplug 147. Although device 102 is depicted with a single micro-via 129,device 102 may have multiple micro-vias. A topside metal electrode 130is formed overlying the piezoelectric layer 120. A top cap structure isbonded to the piezoelectric layer 120. This top cap structure 119includes bond pads which are connected to one or more bond pads 144 andtopside metal 145 on piezoelectric layer 120. The topside metal 145includes a topside metal plug 146.

The thinned substrate 112 has the first and second backside trenches113, 114. A backside metal electrode 131 is formed underlying a portionof the thinned seed substrate 112, the first backside trench 113, andthe topside metal electrode 130. A backside metal plug 147 is formedunderlying a portion of the thinned seed substrate 112, the secondbackside trench 114, and the topside metal plug 146. This backside metalplug 147 is electrically coupled to the topside metal plug 146. Abackside cap structure 162 is bonded to the thinned seed substrate 112,underlying the first and second backside trenches. One or more backsidebond pads (171, 172, 173) are formed within one or more portions of thebackside cap structure 162. Solder balls 170 are electrically coupled tothe one or more backside bond pads 171-173. Further details relating tothe method of manufacture of this device will be discussed starting fromFIG. 14A.

FIG. 1C is a simplified diagram illustrating an acoustic resonatordevice having interposer/cap-free structure interconnections accordingto an example of the present invention. As shown, device 103 includes athinned seed substrate 112 with an overlying single crystalpiezoelectric layer 120, which has a micro-via 129. The micro-via 129can include a topside micro-trench 121, a topside metal plug 146, abackside trench 114, and a backside metal plug 147. Although device 103is depicted with a single micro-via 129, device 103 may have multiplemicro-vias. A topside metal electrode 130 is formed overlying thepiezoelectric layer 120. The thinned substrate 112 has the first andsecond backside trenches 113, 114. A backside metal electrode 131 isformed underlying a portion of the thinned seed substrate 112, the firstbackside trench 113, and the topside metal electrode 130. A backsidemetal plug 147 is formed underlying a portion of the thinned seedsubstrate 112, the second backside trench 114, and the topside metal145. This backside metal plug 147 is electrically coupled to the topsidemetal plug 146 and the backside metal electrode 131. Further detailsrelating to the method of manufacture of this device will be discussedstarting from FIG. 2.

FIG. 1D is a simplified diagram illustrating an acoustic resonatordevice having interposer/cap-free structure interconnections with ashared backside trench according to an example of the present invention.As shown, device 104 includes a thinned seed substrate 112 with anoverlying single crystal piezoelectric layer 120, which has a micro-via129. The micro-via 129 can include a topside micro-trench 121, a topsidemetal plug 146, and a backside metal 147. Although device 104 isdepicted with a single micro-via 129, device 104 may have multiplemicro-vias. A topside metal electrode 130 is formed overlying thepiezoelectric layer 120. The thinned substrate 112 has a first backsidetrench 113. A backside metal electrode 131 is formed underlying aportion of the thinned seed substrate 112, the first backside trench113, and the topside metal electrode 130. A backside metal 147 is formedunderlying a portion of the thinned seed substrate 112, the secondbackside trench 114, and the topside metal 145. This backside metal 147is electrically coupled to the topside metal plug 146 and the backsidemetal electrode 131. Further details relating to the method ofmanufacture of this device will be discussed starting from FIG. 2.

FIGS. 2 and 3 are simplified diagrams illustrating steps for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention. This method illustrates the process forfabricating an acoustic resonator device similar to that shown in FIG.1A. FIG. 2 can represent a method step of providing a partiallyprocessed piezoelectric substrate. As shown, device 102 includes a seedsubstrate 110 with a piezoelectric layer 120 formed overlying. In aspecific example, the seed substrate can include silicon, siliconcarbide, aluminum oxide, or single crystal aluminum gallium nitridematerials, or the like. The piezoelectric layer 120 can include apiezoelectric single crystal layer or a thin film piezoelectric singlecrystal layer.

FIG. 3 can represent a method step of forming a top side metallizationor top resonator metal electrode 130. In a specific example, the topsidemetal electrode 130 can include a molybdenum, aluminum, ruthenium, ortitanium material, or the like and combinations thereof. This layer canbe deposited and patterned on top of the piezoelectric layer by alift-off process, a wet etching process, a dry etching process, a metalprinting process, a metal laminating process, or the like. The lift-offprocess can include a sequential process of lithographic patterning,metal deposition, and lift-off steps to produce the topside metal layer.The wet/dry etching processes can includes sequential processes of metaldeposition, lithographic patterning, metal deposition, and metal etchingsteps to produce the topside metal layer. Those of ordinary skill in theart will recognize other variations, modifications, and alternatives.

FIG. 4A is a simplified diagram illustrating a step for a method ofmanufacture for an acoustic resonator device 401 according to an exampleof the present invention. This figure can represent a method step offorming one or more topside micro-trenches 121 within a portion of thepiezoelectric layer 120. This topside micro-trench 121 can serve as themain interconnect junction between the top and bottom sides of theacoustic membrane, which will be developed in later method steps. In anexample, the topside micro-trench 121 is extends all the way through thepiezoelectric layer 120 and stops in the seed substrate 110. Thistopside micro-trench 121 can be formed through a dry etching process, alaser drilling process, or the like. FIGS. 4B and 4C describe theseoptions in more detail.

FIGS. 4B and 4C are simplified diagrams illustrating alternative methodsfor conducting the method step as described in FIG. 4A. As shown, FIG.4B represents a method step of using a laser drill, which can quicklyand accurately form the topside micro-trench 121 in the piezoelectriclayer 120. In an example, the laser drill can be used to form nominal 50um holes, or holes between 10 um and 500 um in diameter, through thepiezoelectric layer 120 and stop in the seed substrate 110 below theinterface between layers 120 and 110. A protective layer 122 can beformed overlying the piezoelectric layer 120 and the topside metalelectrode 130. This protective layer 122 can serve to protect the devicefrom laser debris and to provide a mask for the etching of the topsidemicro-via 121. In a specific example, the laser drill can be an 11 Whigh power diode-pumped UV laser, or the like. This mask 122 can besubsequently removed before proceeding to other steps. The mask may alsobe omitted from the laser drilling process, and air flow can be used toremove laser debris.

FIG. 4C can represent a method step of using a dry etching process toform the topside micro-trench 121 in the piezoelectric layer 120. Asshown, a lithographic masking layer 123 can be forming overlying thepiezoelectric layer 120 and the topside metal electrode 130. The topsidemicro-trench 121 can be formed by exposure to plasma, or the like.

FIGS. 4D and 4E are simplified diagrams illustrating an alternativemethod for conducting the method step as described in FIG. 4A. Thesefigures can represent the method step of manufacturing multiple acousticresonator devices simultaneously. In FIG. 4D, two devices are shown onDie #1 and Die #2, respectively. FIG. 4E shows the process of forming amicro-via 121 on each of these dies while also etching a scribe line 124or dicing line. In an example, the etching of the scribe line 124singulates and relieves stress in the piezoelectric single crystal layer120.

FIGS. 5 to 8 are simplified diagrams illustrating steps for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention. FIG. 5 can represent the method step of formingone or more bond pads 140 and forming a topside metal 141 electricallycoupled to at least one of the bond pads 140. The topside metal 141 caninclude a topside metal plug 146 formed within the topside micro-trench121. In a specific example, the topside metal plug 146 fills the topsidemicro-trench 121 to form a topside portion of a micro-via.

In an example, the bond pads 140 and the topside metal 141 can include agold material or other interconnect metal material depending upon theapplication of the device. These metal materials can be formed by alift-off process, a wet etching process, a dry etching process, ascreen-printing process, an electroplating process, a metal printingprocess, or the like. In a specific example, the deposited metalmaterials can also serve as bond pads for a cap structure, which will bedescribed below.

FIG. 6 can represent a method step for preparing the acoustic resonatordevice for bonding, which can be a hermetic bonding. As shown, a top capstructure is positioned above the partially processed acoustic resonatordevice as described in the previous figures. The top cap structure canbe formed using an interposer substrate 119 in two configurations: fullyprocessed interposer version 601 (through glass via) and partiallyprocessed interposer version 602 (blind via version). In the 601version, the interposer substrate 119 includes through-via structures151 that extend through the interposer substrate 119 and areelectrically coupled to bottom bond pads 142 and top bond pads 143. Inthe 602 version, the interposer substrate 119 includes blind viastructures 152 that only extend through a portion of the interposersubstrate 119 from the bottom side. These blind via structures 152 arealso electrically coupled to bottom bond pads 142. In a specificexample, the interposer substrate can include a silicon, glass,smart-glass, or other like material.

FIG. 7 can represent a method step of bonding the top cap structure tothe partially processed acoustic resonator device. As shown, theinterposer substrate 119 is bonded to the piezoelectric layer by thebond pads (140, 142) and the topside metal 141, which are now denoted asbond pad 144 and topside metal 145. This bonding process can be doneusing a compression bond method or the like. FIG. 8 can represent amethod step of thinning the seed substrate 110, which is now denoted asthinned seed substrate 111. This substrate thinning process can includegrinding and etching processes or the like. In a specific example, thisprocess can include a wafer backgrinding process followed by stressremoval, which can involve dry etching, CMP polishing, or annealingprocesses.

FIG. 9A is a simplified diagram illustrating a step for a method ofmanufacture for an acoustic resonator device 901 according to an exampleof the present invention. FIG. 9A can represent a method step forforming backside trenches 113 and 114 to allow access to thepiezoelectric layer from the backside of the thinned seed substrate 111.In an example, the first backside trench 113 can be formed within thethinned seed substrate 111 and underlying the topside metal electrode130. The second backside trench 114 can be formed within the thinnedseed substrate 111 and underlying the topside micro-trench 121 andtopside metal plug 146. This substrate is now denoted thinned substrate112. In a specific example, these trenches 113 and 114 can be formedusing deep reactive ion etching (DRIE) processes, Bosch processes, orthe like. The size, shape, and number of the trenches may vary with thedesign of the acoustic resonator device. In various examples, the firstbackside trench may be formed with a trench shape similar to a shape ofthe topside metal electrode or a shape of the backside metal electrode.

The first backside trench may also be formed with a trench shape that isdifferent from both a shape of the topside metal electrode and thebackside metal electrode.

FIGS. 9B and 9C are simplified diagrams illustrating an alternativemethod for conducting the method step as described in FIG. 9A. LikeFIGS. 4D and 4E, these figures can represent the method step ofmanufacturing multiple acoustic resonator devices simultaneously. InFIG. 9B, two devices with cap structures are shown on Die #1 and Die #2,respectively. FIG. 9C shows the process of forming backside trenches(113, 114) on each of these dies while also etching a scribe line 115 ordicing line. In an example, the etching of the scribe line 115 providesan optional way to singulate the backside wafer 112.

FIG. 10 is a simplified diagram illustrating a step for a method ofmanufacture for an acoustic resonator device 1000 according to anexample of the present invention. This figure can represent a methodstep of forming a backside metal electrode 131 and a backside metal plug147 within the backside trenches of the thinned seed substrate 112. Inan example, the backside metal electrode 131 can be formed underlyingone or more portions of the thinned substrate 112, within the firstbackside trench 113, and underlying the topside metal electrode 130.This process completes the resonator structure within the acousticresonator device. The backside metal plug 147 can be formed underlyingone or more portions of the thinned substrate 112, within the secondbackside trench 114, and underlying the topside micro-trench 121. Thebackside metal plug 147 can be electrically coupled to the topside metalplug 146 and the backside metal electrode 131. In a specific example,the backside metal electrode 130 can include a molybdenum, aluminum,ruthenium, or titanium material, or the like and combinations thereof.The backside metal plug can include a gold material, low resistivityinterconnect metals, electrode metals, or the like. These layers can bedeposited using the deposition methods described previously.

FIGS. 11A and 11B are simplified diagrams illustrating alternative stepsfor a method of manufacture for an acoustic resonator device accordingto an example of the present invention. These figures show methods ofbonding a backside cap structure underlying the thinned seed substrate112. In FIG. 11A, the backside cap structure is a dry film cap 161,which can include a permanent photo-imageable dry film such as a soldermask, polyimide, or the like. Bonding this cap structure can becost-effective and reliable, but may not produce a hermetic seal. InFIG. 11B, the backside cap structure is a substrate 162, which caninclude a silicon, glass, or other like material. Bonding this substratecan provide a hermetic seal, but may cost more and require additionalprocesses. Depending upon application, either of these backside capstructures can be bonded underlying the first and second backside vias.

FIGS. 12A to 12E are simplified diagrams illustrating steps for a methodof manufacture for an acoustic resonator device according to an exampleof the present invention. More specifically, these figures describeadditional steps for processing the blind via interposer “602” versionof the top cap structure. FIG. 12A shows an acoustic resonator device1201 with blind vias 152 in the top cap structure. In FIG. 12B, theinterposer substrate 119 is thinned, which forms a thinned interposersubstrate 118, to expose the blind vias 152. This thinning process canbe a combination of a grinding process and etching process as describedfor the thinning of the seed substrate. In FIG. 12C, a redistributionlayer (RDL) process and metallization process can be applied to createtop cap bond pads 160 that are formed overlying the blind vias 152 andare electrically coupled to the blind vias 152. As shown in FIG. 12D, aball grid array (BGA) process can be applied to form solder balls 170overlying and electrically coupled to the top cap bond pads 160. Thisprocess leaves the acoustic resonator device ready for wire bonding 171,as shown in FIG. 12E.

FIG. 13 is a simplified diagram illustrating a step for a method ofmanufacture for an acoustic resonator device according to an example ofthe present invention. As shown, device 1300 includes two fullyprocessed acoustic resonator devices that are ready to singulation tocreate separate devices. In an example, the die singulation process canbe done using a wafer dicing saw process, a laser cut singulationprocess, or other processes and combinations thereof.

FIGS. 14A to 14G are simplified diagrams illustrating steps for a methodof manufacture for an acoustic resonator device according to an exampleof the present invention. This method illustrates the process forfabricating an acoustic resonator device similar to that shown in FIG.1B. The method for this example of an acoustic resonator can go throughsimilar steps as described in FIGS. 1-5. FIG. 14A shows where thismethod differs from that described previously. Here, the top capstructure substrate 119 and only includes one layer of metallizationwith one or more bottom bond pads 142. Compared to FIG. 6, there are novia structures in the top cap structure because the interconnectionswill be formed on the bottom side of the acoustic resonator device.

FIGS. 14B to 14F depict method steps similar to those described in thefirst process flow. FIG. 14B can represent a method step of bonding thetop cap structure to the piezoelectric layer 120 through the bond pads(140, 142) and the topside metal 141, now denoted as bond pads 144 andtopside metal 145 with topside metal plug 146. FIG. 14C can represent amethod step of thinning the seed substrate 110, which forms a thinnedseed substrate 111, similar to that described in FIG. 8. FIG. 14D canrepresent a method step of forming first and second backside trenches,similar to that described in FIG. 9A. FIG. 14E can represent a methodstep of forming a backside metal electrode 131 and a backside metal plug147, similar to that described in FIG. 10. FIG. 14F can represent amethod step of bonding a backside cap structure 162, similar to thatdescribed in FIGS. 11A and 11B.

FIG. 14G shows another step that differs from the previously describedprocess flow. Here, the backside bond pads 171, 172, and 173 are formedwithin the backside cap structure 162. In an example, these backsidebond pads 171-173 can be formed through a masking, etching, and metaldeposition processes similar to those used to form the other metalmaterials. A BGA process can be applied to form solder balls 170 incontact with these backside bond pads 171-173, which prepares theacoustic resonator device 1407 for wire bonding.

FIGS. 15A to 15E are simplified diagrams illustrating steps for a methodof manufacture for an acoustic resonator device according to an exampleof the present invention.

This method illustrates the process for fabricating an acousticresonator device similar to that shown in FIG. 1B. The method for thisexample can go through similar steps as described in FIG. 1-5. FIG. 15Ashows where this method differs from that described previously. Atemporary carrier 218 with a layer of temporary adhesive 217 is attachedto the substrate. In a specific example, the temporary carrier 218 caninclude a glass wafer, a silicon wafer, or other wafer and the like.

FIGS. 15B to 15F depict method steps similar to those described in thefirst process flow. FIG. 15B can represent a method step of thinning theseed substrate 110, which forms a thinned substrate 111, similar to thatdescribed in FIG. 8. In a specific example, the thinning of the seedsubstrate 110 can include a back side grinding process followed by astress removal process. The stress removal process can include a dryetch, a Chemical Mechanical Planarization (CMP), and annealingprocesses.

FIG. 15C can represent a method step of forming a shared backside trench113, similar to the techniques described in FIG. 9A. The main differenceis that the shared backside trench is configured underlying both topsidemetal electrode 130, topside micro-trench 121, and topside metal plug146. In an example, the shared backside trench 113 is a backsideresonator cavity that can vary in size, shape (all possible geometricshapes), and side wall profile (tapered convex, tapered concave, orright angle). In a specific example, the forming of the shared backsidetrench 113 can include a litho-etch process, which can include aback-to-front alignment and dry etch of the backside substrate 111. Thepiezoelectric layer 120 can serve as an etch stop layer for the formingof the shared backside trench 113.

FIG. 15D can represent a method step of forming a backside metalelectrode 131 and a backside metal 147, similar to that described inFIG. 10. In an example, the forming of the backside metal electrode 131can include a deposition and patterning of metal materials within theshared backside trench 113. Here, the backside metal 131 serves as anelectrode and the backside plug/connect metal 147 within the micro-via121. The thickness, shape, and type of metal can vary as a function ofthe resonator/filter design. As an example, the backside electrode 131and via plug metal 147 can be different metals. In a specific example,these backside metals 131, 147 can either be deposited and patterned onthe surface of the piezoelectric layer 120 or rerouted to the backsideof the substrate 112. In an example, the backside metal electrode may bepatterned such that it is configured within the boundaries of the sharedbackside trench such that the backside metal electrode does not come incontact with one or more side-walls of the seed substrate created duringthe forming of the shared backside trench.

FIG. 15E can represent a method step of bonding a backside cap structure162, similar to that described in FIGS. 11A and 11B, following ade-bonding of the temporary carrier 218 and cleaning of the topside ofthe device to remove the temporary adhesive 217. Those of ordinary skillin the art will recognize other variations, modifications, andalternatives of the methods steps described previously.

According to an example, the present invention includes a method forforming a piezoelectric layer to fabricate an acoustic resonator device.More specifically, the present method includes forming a single crystalmaterial to be used to fabricate the acoustic resonator device. Bymodifying the strain state of the III-Nitride (III-N) crystal lattice,the present method can change the piezoelectric properties of the singlecrystal material to adjust the acoustic properties of subsequent devicesfabricated from this material. In a specific example, the method forforming the strained single crystal material can include modification ofgrowth conditions of individual layers by employing one or a combinationof the following parameters; gas phase reactant ratios, growth pressure,growth temperature, and introduction of impurities.

In an example, the single crystal material is grown epitaxially upon asubstrate. Methods for growing the single crystal material can includemetal-organic chemical vapor deposition (MOCVD), molecular beam epitaxy(MBE), hydride vapor phase epitaxy (HVPE), atomic layer deposition(ALD), or the like. Various process conditions can be selectively variedto change the piezoelectric properties of the single crystal material.These process conditions can include temperature, pressure, layerthickness, gas phase ratios, and the like. For example, the temperatureconditions for films containing aluminum (Al) and gallium (Ga) and theiralloys can range from about 800 to about 1500 degrees Celsius. Thetemperature conditions for films containing Al, Ga, and indium (In) andtheir alloys can range from about 600 to about 1000 degrees Celsius. Inanother example, the pressure conditions for films containing Al, Ga,and In and their alloys can range from about 1E-4 Torr to about 900Torr.

FIG. 16 is a flow diagram illustrating a method for manufacturing anacoustic resonator device according to an example of the presentinvention. The following steps are merely examples and should not undulylimit the scope of the claims herein. One of ordinary skill in the artwould recognize many other variations, modifications, and alternatives.For example, various steps outlined below may be added, removed,modified, rearranged, repeated, and/or overlapped, as contemplatedwithin the scope of the invention. A typical growth process 1600 can beoutlined as follows:

1601. Provide a substrate having the required material properties andcrystallographic orientation. Various substrates can be used in thepresent method for fabricating an acoustic resonator device such asSilicon, Sapphire, Silicon Carbide, Gallium Nitride (GaN) or AluminumNitride (AlN) bulk substrates. The present method can also use GaNtemplates, AlN templates, and Al_(x)Ga_(1-x)N templates (where x variesbetween 0.0 and 1.0).

-   -   These substrates and templates can have polar, non-polar, or        semi-polar crystallographic orientations. Those of ordinary        skill in the art will recognize other variations, modifications,        and alternatives;

1602. Place the selected substrate into a processing chamber within acontrolled environment;

1603. Heat the substrate to a first desired temperature. At a reducedpressure between 5-800 mbar the substrates are heated to a temperaturein the range of 1100°-1350° C. in the presence of purified hydrogen gasas a means to clean the exposed surface of the substrate. The purifiedhydrogen flow shall be in the range of 5-30 slpm (standard liter perminute) and the purity of the gas should exceed 99.9995%;

1604. Cool the substrate to a second desired temperature. After 10-15minutes at elevated temperature, the substrate surface temperatureshould be reduced by 100-200° C.; the temperature offset here isdetermined by the selection of substrate material and the initial layerto be grown (Highlighted in FIGS. 18A-C);

1605. Introduce reactants to the processing chamber. After thetemperature has stabilized the Group III and Group V reactants areintroduced to the processing chamber and growth is initiated.

1606. Upon completion of the nucleation layer the growth chamberpressures, temperatures, and gas phase mixtures may be further adjustedto grow the layer or plurality of layers of interest for the acousticresonator device.

1607. During the film growth process the strain-state of the materialmay be modulated via the modification of growth conditions or by thecontrolled introduction of impurities into the film (as opposed to themodification of the electrical properties of the film).

1608. At the conclusion of the growth process the Group III reactantsare turned off and the temperature resulting film or films arecontrollably lowered to room. The rate of thermal change is dependentupon the layer or plurality of layers grown and in the preferredembodiment is balanced such that the physical parameters of thesubstrate including films are suitable for subsequent processing.

Referring to step 1605, the growth of the single crystal material can beinitiated on a substrate through one of several growth methods: directgrowth upon a nucleation layer, growth upon a super lattice nucleationlayer, and growth upon a graded transition nucleation layer. The growthof the single crystal material can be homoepitaxial, heteroepitaxial, orthe like. In the homoepitaxial method, there is a minimal latticemismatch between the substrate and the films such as the case for anative III-N single crystal substrate material. In the heteroepitaxialmethod, there is a variable lattice mismatch between substrate and filmbased on in-plane lattice parameters. As further described below, thecombinations of layers in the nucleation layer can be used to engineerstrain in the subsequently formed structure.

Referring to step 1606, various substrates can be used in the presentmethod for fabricating an acoustic resonator device. Silicon substratesof various crystallographic orientations may be used. Additionally, thepresent method can use sapphire substrates, silicon carbide substrates,gallium nitride (GaN) bulk substrates, or aluminum nitride (AlN) bulksubstrates. The present method can also use GaN templates, AINtemplates, and Al_(x)Ga_(1-x)N templates (where x varies between 0.0 and1.0). These substrates and templates can have polar, non-polar, orsemi-polar crystallographic orientations. Those of ordinary skill in theart will recognize other variations, modifications, and alternatives.

In an example, the present method involves controlling materialcharacteristics of the nucleation and piezoelectric layer(s). In aspecific example, these layers can include single crystal materials thatare configured with defect densities of less than 1E+11 defects persquare centimeter. The single crystal materials can include alloysselected from at least one of the following: AlN, AlGaN, GaN, InN,InGaN, AlInN, AlInGaN, and BN. In various examples, any single orcombination of the aforementioned materials can be used for thenucleation layer(s) and/or the piezoelectric layer(s) of the devicestructure.

According to an example, the present method involves strain engineeringvia growth parameter modification. More specifically, the methodinvolves changing the piezoelectric properties of the epitaxial films inthe piezoelectric layer via modification of the film growth conditions(these modifications can be measured and compared via the sound velocityof the piezoelectric films). These growth conditions can includenucleation conditions and piezoelectric layer conditions. The nucleationconditions can include temperature, thickness, growth rate, gas phaseratio (V/III), and the like. The piezo electric layer conditions caninclude transition conditions from the nucleation layer, growthtemperature, layer thickness, growth rate, gas phase ratio (V/III), postgrowth annealing, and the like. Further details of the present methodcan be found below.

FIG. 17 is a simplified graph illustrating the results of forming apiezoelectric layer for an acoustic resonator device according to anexample of the present invention. This graph highlights the ability ofto tailor the acoustic properties of the material for a given Aluminummole fraction. Referring to step 1607 above, such flexibility allows forthe resulting resonator properties to be tailored to the individualapplication. As shown, graph 1700 depicts a plot of acoustic velocity(m/s) over aluminum mole fraction (%). The marked region 1720 shows themodulation of acoustic velocity via strain engineering of the piezoelectric layer at an aluminum mole fraction of 0.4. Here, the data showsthat the change in acoustic velocity ranges from about 7,500 m/s toabout 9,500 m/s, which is about ±1,000 m/s around the initial acousticvelocity of 8,500 m/s. Thus, the modification of the growth parametersprovides a large tunable range for acoustic velocity of the acousticresonator device. This tunable range will be present for all aluminummole fractions from 0 to 1.0 and is a degree of freedom not present inother conventional embodiments of this technology.

The present method also includes strain engineering by impurityintroduction, or doping, to impact the rate at which a sound wave willpropagate through the material. Referring to step 1607 above, impuritiescan be specifically introduced to enhance the rate at which a sound wavewill propagate through the material. In an example, the impurity speciescan include, but is not limited to, the following: silicon (Si),magnesium (Mg), carbon (C), oxygen (O), erbium (Er), rubidium (Rb),strontium (Sr), scandium (Sc), beryllium (Be), molybdenum (Mo),zirconium (Zr), Hafnium (Hf), and vanadium (Va). Silicon, magnesium,carbon, and oxygen are common impurities used in the growth process, theconcentrations of which can be varied for different piezoelectricproperties. In a specific example, the impurity concentration rangesfrom about 1E+10 to about 1E+21 per cubic centimeter. The impuritysource used to deliver the impurities to can be a source gas, which canbe delivered directly, after being derived from an organometallicsource, or through other like processes.

The present method also includes strain engineering by the introductionof alloying elements, to impact the rate at which a sound wave willpropagate through the material. Referring to step 1607 above, alloyingelements can be specifically introduced to enhance the rate at which asound wave will propagate through the material. In an example, thealloying elements can include, but are not limited to, the following:magnesium (Mg), erbium (Er), rubidium (Rb), strontium (Sr), scandium(Sc), titanium (Ti), zirconium (Zr), Hafnium (Hf), vanadium (Va),Niobium (Nb), and tantalum (Ta). In a specific embodiment, the alloyingelement (ternary alloys) or elements (in the case of quaternary alloys)concentration ranges from about 0.01% to about 50%. Similar to theabove, the alloy source used to deliver the alloying elements can be asource gas, which can be delivered directly, after being derived from anorganometallic source, or through other like processes. Those ofordinary skill in the art will recognize other variations,modifications, and alternatives to these processes.

The methods for introducing impurities can be during film growth(in-situ) or post growth (ex-situ). During film growth, the methods forimpurity introduction can include bulk doping, delta doping, co-doping,and the like. For bulk doping, a flow process can be used to create auniform dopant incorporation. For delta doping, flow processes can beintentionally manipulated for localized areas of higher dopantincorporation. For co-doping, the any doping methods can be used tosimultaneously introduce more than one dopant species during the filmgrowth process. Following film growth, the methods for impurityintroduction can include ion implantation, chemical treatment, surfacemodification, diffusion, co-doping, or the like. The of ordinary skillin the art will recognize other variations, modifications, andalternatives.

FIG. 18A is a simplified diagram illustrating a method for forming apiezoelectric layer for an acoustic resonator device according to anexample of the present invention. As shown in device 1801, thepiezoelectric layer 1831, or film, is directly grown on the nucleationlayer 1821, which is formed overlying a surface region of a substrate1810. The nucleation layer 1821 may be the same or different atomiccomposition as the piezoelectric layer 1831. Here, the piezoelectricfilm 1831 may be doped by one or more species during the growth(in-situ) or post-growth (ex-situ) as described previously.

FIG. 18B is a simplified diagram illustrating a method for forming apiezoelectric layer for an acoustic resonator device according to anexample of the present invention. As shown in device 1802, thepiezoelectric layer 1832, or film, is grown on a super latticenucleation layer 1822, which is comprised of layer with alternatingcomposition and thickness. This super lattice layer 1822 is formedoverlying a surface region of the substrate 1810. The strain of device1802 can be tailored by the number of periods, or alternating pairs, inthe super lattice layer 1822 or by changing the atomic composition ofthe constituent layers. Similarly, the piezoelectric film 1832 may bedoped by one or more species during the growth (in-situ) or post-growth(ex-situ) as described previously.

FIG. 18C is a simplified diagram illustrating a method for forming apiezoelectric layer for an acoustic resonator device according to anexample of the present invention. As shown in device 1803, thepiezoelectric layer 1833, or film, is grown on graded transition layers1823. These transition layers 1823, which are formed overlying a surfaceregion of the substrate 1810, can be used to tailor the strain of device1803. In an example, the alloy (binary or ternary) content can bedecreased as a function of growth in the growth direction. This functionmay be linear, step-wise, or continuous. Similarly, the piezoelectricfilm 1833 may be doped by one or more species during the growth(in-situ) or post-growth (ex-situ) as described previously.

In an example, the present invention provides a method for manufacturingan acoustic resonator device. As described previously, the method caninclude a piezoelectric film growth process such as a direct growth upona nucleation layer, growth upon a super lattice nucleation layer, or agrowth upon graded transition nucleation layers. Each process can usenucleation layers that include, but are not limited to, materials oralloys having at least one of the following: AlN, AlGaN, GaN, InN,InGaN, AlInN, AlInGaN, and BN. Those of ordinary skill in the art willrecognize other variations, modifications, and alternatives.

One or more benefits are achieved over pre-existing techniques using theinvention. In particular, the present device can be manufactured in arelatively simple and cost effective manner while using conventionalmaterials and/or methods according to one of ordinary skill in the art.Using the present method, one can create a reliable single crystal basedacoustic resonator using multiple ways of three-dimensional stackingthrough a wafer level process. Such filters or resonators can beimplemented in an RF filter device, an RF filter system, or the like.Depending upon the embodiment, one or more of these benefits may beachieved. Of course, there can be other variations, modifications, andalternatives.

While the above is a full description of the specific embodiments,various modifications, alternative constructions and equivalents may beused. As an example, the packaged device can include any combination ofelements described above, as well as outside of the presentspecification. As used herein, the term “substrate” can mean the bulksubstrate or can include overlying growth structures such as analuminum, gallium, or ternary compound of aluminum and gallium andnitrogen containing epitaxial region, or functional regions,combinations, and the like. Therefore, the above description andillustrations should not be taken as limiting the scope of the presentinvention which is defined by the appended claims.

What is claimed is:
 1. A method for fabricating an acoustic resonatordevice, the method comprising: providing a seed substrate, the seedsubstrate being characterized a substrate crystallographic orientation;placing the seed substrate within a processing chamber having acontrolled environment; heating the seed substrate to a first desiredtemperature; cooling the seed substrate to a second desired temperature;introducing reactants to the processing chamber to start a piezoelectricfilm growth process; adjusting the conditions of the processing chamberto form the piezoelectric film; modulating a strain state of thepiezoelectric film; turning off the reactants; and reducing thetemperature of the processing chamber to room temperature.
 2. The methodof claim 1 wherein the seed substrate is selected from one of thefollowing: a silicon substrate, a sapphire substrate, silicon carbidesubstrate, a GaN bulk substrate, a GaN template, an AlN bulk, an AlNtemplate, and an Al_(x)Ga_(1-x)N template; and wherein the substratecrystallographic orientation includes a polar, non-polar, or semi-polarcrystallographic orientation.
 3. The method of claim 1 wherein heatingthe seed substrate to the first desired temperature includes introducinga purified hydrogen gas to the processing chamber and heating the seedsubstrate in the range of about 1100 to 1350 degrees Celsius at areduced pressure between 5-800 mbar.
 4. The method of claim 3 whereinthe purified hydrogen gas is introduced in the range of 5-30 slpm andthe purity of the hydrogen gas is greater than 99.9995%.
 5. The methodof claim 1 wherein cooling the seed substrate includes cooling the seedsubstrate by 100-200 degrees Celsius.
 6. The method of claim 1 whereinintroducing the reactants includes introducing Group III and Group Vreactants.
 7. The method of claim 1 wherein the piezoelectric filmgrowth process can include a direct growth upon a nucleation layer,growth upon a super lattice nucleation layer, or a growth upon gradedtransition nucleation layers; wherein the super lattice nucleation layerincludes alternating pairs of nucleation layers; and wherein thenucleation layer, each layer of the graded transition nucleation layers,and each nucleation layer within the super lattice nucleation layer caninclude materials or alloys having at least one of the following: AlN,AlGaN, GaN, AlScN, InN, InGaN, AlInN, AlInGaN, and BN.
 8. The method ofclaim 1 wherein the modulating of the strain state includes modifyingone or more growth conditions of the piezoelectric film resulting in thestrained single crystal piezoelectric layer having an acoustic velocitycharacteristic with a modulated range of ±1000 m/s.
 9. The method ofclaim 1 wherein the modulating of the strain state includes introducingone or more impurities into the piezoelectric film; wherein the one ormore impurity species can include the following: silicon (Si), magnesium(Mg), carbon (C), oxygen (0), erbium (Er), rubidium (Rb), strontium(Sr), scandium (Sc), beryllium (Be), molybdenum (Mo), zirconium (Zr),Hafnium (Hf), and vanadium (Va); wherein the one or more impurityspecies has impurity concentrations ranging from about 1E+10 to about1E+21 per cubic centimeter; and wherein introducing one or moreimpurities includes using a gas source to directly deliver the one ormore impurity species or using an organometallic source to derive thesource gas to deliver the one or more impurity species.
 10. The methodof claim 1 wherein the modulating of the strain state includesintroducing one or more alloying elements into the piezoelectric film;wherein the alloying elements can include the following: magnesium (Mg),erbium (Er), rubidium (Rb), strontium (Sr), scandium (Sc), titanium(Ti), zirconium (Zr), Hafnium (Hf), vanadium (Va), Niobium (Nb), andtantalum (Ta); wherein the alloying element (ternary alloys) or elements(in the case of quaternary alloys) has concentrations ranging from about0.01% to about 50%; and wherein introducing one or more alloyingelements includes using a gas source to directly deliver the one or morealloying elements or using an organometallic source to derive the sourcegas to deliver the one or more alloying elements.
 11. A method forfabricating an acoustic resonator device, the method comprising: placinga substrate having a substrate surface region within a processingchamber having a controlled environment; forming a nucleation layeroverlying the substrate surface region; introducing reactants to theprocessing chamber to start a piezoelectric film growth process;adjusting a temperature and a pressure of the processing chamber to formthe piezoelectric film; and modulating a strain state of thepiezoelectric film to form a strained single crystal piezoelectric filmhaving an acoustic velocity characteristic with a modulated range of±1000 m/s.
 12. The method of claim 11 wherein the substrate is selectedfrom one of the following: a silicon substrate, a sapphire substrate,silicon carbide substrate, a GaN bulk substrate, a GaN template, an AINbulk, an AIN template, and an Al_(x)Ga_(1-x)N template.
 13. The methodof claim 11 wherein the piezoelectric film growth process is selectedfrom one of the following: metal-organic chemical vapor deposition(MOCVD), molecular beam epitaxy (MBE), hydride vapor phase epitaxy(HVPE), physical vapor phase deposition (PVD), and atomic layerdeposition (ALD).
 14. The method of claim 11 wherein the nucleationlayer and the strained single crystal piezoelectric film includematerials or alloys having at least one of the following: AN, AlGaN,GaN, AlScN, InN, InGaN, AlInN, AlInGaN, and BN.
 15. The method of claim11 wherein introducing the reactants includes introducing Group III andGroup V reactants.
 16. The method of claim 11 further comprisingintroducing a purified hydrogen gas to the processing chamber afterplacing the substrate; heating the substrate in the range of about 1100to 1350 degrees Celsius at a reduced pressure between 5-800 mbar in thepresence of the purified hydrogen gas; and cooling the substrate byabout 100 to 200 degrees Celsius after heating the substrate.
 17. Themethod of claim 11 further comprising turning off the reactants andreducing the temperature of the processing chamber to room temperatureafter modulating the strain state of the piezoelectric film.
 18. Themethod of claim 11 wherein the modulating of the strain state includesintroducing one or more impurities into the piezoelectric film; whereinthe one or more impurity species can include the following: silicon(Si), magnesium (Mg), carbon (C), oxygen (0), erbium (Er), rubidium(Rb), strontium (Sr), scandium (Sc), beryllium (Be), molybdenum (Mo),zirconium (Zr), Hafnium (Hf), and vanadium (Va); wherein the one or moreimpurity species has impurity concentrations ranging from about 1E+10 toabout 1E+21 per cubic centimeter; and wherein introducing one or moreimpurities includes using a gas source to directly deliver the one ormore impurity species or using an organometallic source to derive thesource gas to deliver the one or more impurity species.
 19. The methodof claim 11 wherein the modulating of the strain state includesintroducing one or more alloying elements into the piezoelectric film;wherein the alloying elements can include the following: magnesium (Mg),erbium (Er), rubidium (Rb), strontium (Sr), scandium (Sc), titanium(Ti), zirconium (Zr), Hafnium (Hf), vanadium (Va), Niobium (Nb), andtantalum (Ta); wherein the alloying element (ternary alloys) or elements(in the case of quaternary alloys) has concentrations ranging from about0.01% to about 50%; and wherein introducing one or more alloyingelements includes using a gas source to directly deliver the one or morealloying elements or using an organometallic source to derive the sourcegas to deliver the one or more alloying elements.
 20. A method forfabricating an acoustic resonator device, the method comprising: placinga substrate having a substrate surface region within a processingchamber having a controlled environment; forming a nucleation layeroverlying the substrate surface region; introducing reactants to theprocessing chamber to start a piezoelectric film growth process;adjusting the processing chamber to a temperature ranging from 600degrees Celsius to 1500 degrees Celsius and a pressure ranging from 1E-4Torr to 900 Torr to form the piezoelectric film; and modulating a strainstate of the piezoelectric film by introducing one or more impurities orone or more alloying elements to form a strained single crystalpiezoelectric film having an acoustic velocity characteristic with amodulated range of ±1000 m/s.